1. Field of the Invention
The present invention relates to an ink-jet recording process carried out by using a recording liquid (hereinafter simply referred to as an "ink") of a pigment type, and to an ink of a pigment type thereof.
2. Description of the Prior Art
Among the known various recording processes, the so-called ink-jet recording process is recognized as an extremely useful recording process, since the recording can be carried out at non-impact without generating noise and at high speed, and made on plain paper without any particular fixing treatment. Heretofore, various ink-jet recording processes have been proposed. Some are used in practice and some are still under development.
In the ink-jet recording process, recording is carried out by a process in which droplets of a recording liquid called an ink are flown by various actuating principles to deposit onto an image recording member such as paper, and the like. And in the ink-jet recording process, several processes for forming droplets are used. An embodiment is shown in FIG. 1.
FIG. 1 shows an apparatus in which a recording signal is applied to a recording heat section having a piezo-oscillator and droplets of a recording liquid are generated according to the signal to effect recording. In FIG. 1, a recording head 1 is provided with a piezo-oscillator 2a, a vibrator 2b, an inlet 3 for a recording liquid, a liquid chamber 4 in the head and a liquid ejecting portion (ejecting orifice) 5. A recording liquid 7 stored in a storage tank 6 is introduced into liquid chamber 4 through a feed pipe 8. If necessary, feed pipe 8 may be provided with intermediate treating means 9 such as pumps, filters, and the like. To piezo-oscillator 2a is applied a signal which is transduced from a recording signal S to a pulse by signal proceeding means 10 (for example pulse transducer) to generate pressure change for a recording liquid in liquid chamber 4 according to the signal. As the result, recording liquid 7 is ejected as droplets 11 from ejecting orifice 5 to effect recording on surface of an image recording member 12.
There are known various apparatuses other than the abovementioned apparatus. For example, FIG. 2 shows a modified embodiment of that in FIG. 1. In the modified embodiment, a liquid chamber 4 is of a nozzle form, and around it is a cylindrical piezo-oscillator (in this apparatus, a mechanism generating droplets is essentially the same as that shown in FIG. 1). Also known are an apparatus in which charged droplets are continuously generated in order to use a portion of the droplets for recording, another apparatus in which heat energy corresponding to a recording signal is applied to a recording liquid in a chamber of a recording head inorder to generate droplets by the heat energy, and the like.
An embodiment is shown in FIGS. 3A, 3B, and 4.
A head 13 is manufactured by jointing a plate such as glass, ceramics, plastics, and the like, having a groove 14 to a heat-generating head 15 used for a heat-sensitive recording process (in FIGS. 3A and 3B, a thin film head is shown, however a heat-generating head is not restricted to this construction). Heat-generating head 15 is constituted of a protective film 16 made of silicon oxide and the like, aluminum electrodes 17-1 and 17-2, a resistive heater layer 18 made of nichrome and the like, a heat-accumulating layer 19, and a substrate 20 having an excellent heat-releasing property such as alumina and the like.
An ink 21 arrives at an ejecting orific 22, so that a meniscus 23 is formed by a pressure P.
When an electric signal is applied to electrodes 17-1 and 17-2, a region represented by a character n generates suddenly heat to generate bubbles in an ink 21 contacting with n. Meniscus 23 is projected by the pressure. Recording droplets 24 of ink 21 are ejected from orifice 22 to fly toward an image recording material 25. FIG. 4 shows an appearance view of a multi head in which a large number of heads shown in FIG. 3A are arrayed. The multi head is manufactured by jointing a glass plate 27 having a large number of grooves 26 to a heat-generating head 28 similar to that described in FIG. 3A.
FIG. 3A is a sectional view of head 13 and is taken along the ink flow-path. FIG. 3B is a sectional view of FIG. 3A, the view being taken along A-B of FIG. 3A.
An ink applied to the abovementioned ink-jet recording process essentially comprises dye and a solvent therefor. The ink characteristics are considerably dependent upon the characteristics of the dye. Therefore, when an ink-jet recording is carried out by using an ink which contains mainly a water-soluble dye, properties of the obtained ink images depend upon the properties of the water-soluble dye. Accordingly, the ink images are inferior in water-resistance and light fastness. Storage stability of an ink per se containing such water-soluble dye is not so excellent. For these reasons, instead of such dye type ink, an ink-jet recording process has been recently proposed in which a pigment-type ink is used. The pigment-type ink has the advantages that images obtained by the pigment-type ink are extremely excellent in water resistance and light fastness in comparison with images obtained by the dye-type ink. However, since pigment is insoluble in mediums for the ink, complex techniques are required to achieve fine dispersion in the ink, and it is very difficult to enhance the stability of the dispersion.
Further, in ink-jet recording processes, the ink to be used is required to meet the following:
the ink has physical properties (viscosity, surface-tension, electrical conductivity, and the like) of the liquid, which agree with ejecting conditions (driving voltage and driving frequency for a piezo-element, form, size, and material of an ejecting orifice, and the like; and the ink has excellent storage stability for a long period and does not clog in an ink-jet apparatus
fixing toward image recording material (paper, fabric, film etc.) can be carried out speedily and surely, a printed dot is smooth at the border thereof, and spreading of the ink is slight;
the printed ink images are clear in color tone and have high density;
the printed ink images are excellent in water resistance and light fastness;
the ink does not corrode materials (storage tank, connection tube, seal, etc.) which contact with the ink; and
the ink is essentially odorless and harmless, and excellent in safety such as inflammability and the like.
Further, in case the image receiving materials are fabric, washing (including dry cleaning) resistance is required.
It is considerably difficult to satisfy simultaneously the abovamentioned characteristics. The conventional techniques are unsatisfactory to these points.